Not applicable.
Not Applicable.
The invention relates generally to surgical devices for dissecting bone and tissue, and to methods pertaining thereto. More particularly, this invention relates to a surgical cutting instrument useful in performing craniotomies, and a footed attachment for such an instrument.
A craniotomy involves the surgical removal of a section of bone from the skull for the purpose of operating on the underlying tissues, usually the brain. When the surgeon has completed the surgery to the target tissue, the removed section of bone, called the bone flap, is replaced and the skull is allowed to heal.
A craniotomy may be required in cases of trauma, infection, and tumor growth within the skull. Some of the abnormalities that may require a craniotomy include various lesions affecting the skull and brain. Examples of these lesions include: benign tumors of the skull; tumors of the gliomas, the supporting cells of the brain; cancers from other organs that have metastasized to the brain; abscesses, or localized infections; and, meningiomas, benign tumors of the meninges that, if allowed to grow, may compress the brain and cause damage. Other abnormalities may include aneurysms that can rupture and cause hemorrhaging around the brain, and arteriovenous malformations, such as abnormal tangling of the arteries and veins that may bleed and cause a clot within the brain. Patients with high blood pressure may be at risk of rupturing a blood vessel within the brain, resulting in intracerebral hematoma. Another abnormality includes hydrocephalus, which can result from obstruction to the flow of cerebrospinal fluid that bathes the brain. Patients suffering from any of these skull and brain abnormalities may require a craniotomy to treat or remove the affected area.
Surgical cutting instruments, called craniotomes, have been employed for performing these cranial surgeries. Craniotomes typically have a rotating blade or burr at one end and a handle or grip at the opposite end. Most of these cutting tools also have a guard attached to the cutting end to prevent the instrument from penetrating too far into the skull and damaging the underlying membranes.
The procedure for removing the bone flap involves drilling a series of small holes, called burr holes or pilot holes, in the skull. Usually, three holes are drilled at an angle perpendicular to the surface of the cranium. The holes are positioned around the periphery of the proposed bone flap. A craniotome is then used to cut the bone between each adjacent hole in a progressive manner until the bone flap is separated from the surrounding skull. The guard attached to the craniotome prevents the rotating saw from penetrating the dura, the membrane protecting the brain, into the brain itself, which could lead to severe damage. After the bone flap is removed, the surgeon can access the specific lesion or abnormality that is found and perform the necessary surgery. When the surgery is complete, the bone flap is replaced and anchored to the skull with wire sutures, titanium plates and screws, or adhesives. Small titanium plates are used to cover the pilot holes, and the skull is allowed to heal.
Alternatively, titanium plates can be attached to the bone flap before its removal from the skull. After the step of drilling the pilot holes, small titanium plates having multiple screw holes can be attached to the bone flap near these pilot holes. The plate can be attached to the bone flap with a single screw. A plurality of plates can be attached to the bone flap, whereby each plate is attached to the bone flap so as to cover a pilot hole bordering the flap.
To release the bone flap for access to the underlying tissue, the surgeon maneuvers the plates away from the cutting line while using the craniotome to cut between the pilot holes. The plates attached to the bone flap can prevent the flap from falling into the void. When the intracranial procedure is done, the bone flap can be replaced and the titanium plates reoriented to cover the pilot holes. The remaining screw holes of the plates are then screwed in to provide anchorage and rigid fixation of the bone flap to the skull.
In these standard craniotomy procedures, heavy reliance is placed on the fixation system to hold the bone flap in place until natural healing of the bone occurs. is Since the bone flap and the hole have straight edges, i.e., edges that are perpendicular to the surface of the cranium, the bone flap could potentially fall into the hole or out of the skull when the patient moves. Such a system is inherently unstable and requires the use of external fixation means to keep the bone flap in place. Because external fixation means can often increase the amount of pain and trauma experienced by the patient, prolong the duration of the surgical procedure, lead to unnecessary and avoidable scarring, and inconvenience the patient with time-consuming return visits to the surgeon to have the fixation means removed, there exists a need for an inherently stable system that eliminates the need for, or requires less external fixation means, than what is currently available.
The present invention overcomes the drawbacks inherent in prior art surgical methods and devices by providing a guard device with an angled cranium guide that can be removably and replaceably attached to an existing craniotome for producing a stable bone flap system. The dura guard includes an elongate stem defining a longitudinal axis between a proximal end and a distal end. At the proximal end of the stem the dura guard is adapted for attachment to the craniotome. A footplate extends from the distal end of the stem at an angle with respect to the longitudinal axis of the stem. The footplate is positioned adjacent to, but spaced apart from, the cutting portion of the craniotome and prevents the cutting portion from penetrating too far into the skull, potentially damaging the dura. On one side of the stem, positioned between the proximal and distal ends, is an angled cranium guide that extends from the stem and faces away from the cutting portion of the craniotome. The dura guard with its angled cranium guide enables the surgeon to rest the cranium guide upon the surface of the cranium and maintain the craniotome at a fixed angle while cutting the skull. By holding the craniotome at a steady angle, the surgeon is able to produce a consistent, bevel-edged bone flap and hole having angled edges or walls. The angled edges of the hole in the cranium and the angled edges of the bone flap enable the flap to reattach to the hole in a stable fashion.
In one embodiment of the present invention, the footplate of the dura guard is obtusely angled with respect to its stem. The angle of the footplate with respect to the stem can be set at the same as the angle of the cranium guide to the stem. In an alternative embodiment, the footplate can extend at a different angle than the cranium guide. For example, the footplate can extend perpendicular to the stem. In yet another embodiment, the stem extends parallel to the cutting portion of the craniotome, but could also extend at an angle to the cutting portion.
The present invention also encompasses a method for using a craniotome with a dura guard having an angled cranium guide. The method comprises the steps of providing a craniotome having attached thereto a dura guard with an angled cranium guide, resting the cranium guide against the surface of the skull, guiding the craniotome forward at a fixed angle along the bone surface, and creating an angled cut so as to produce a bevel-cut bone flap. The bone flap is replaced after cranial surgery, and allowed to heal. Fixation systems known in the art such as titanium plates and screws, wire sutures, or adhesives can optionally be used to anchor the bone flap to the skull.
Further features of the invention, its nature and various advantages, will be more apparent from the accompanying drawings and the following detailed description of the drawings and the preferred embodiments.